The present invention relates to compositions and methods of making concrete, mortar and grout, and more specifically low density cellular concretes which harden in an accelerated period of time.
Cementitious products such as concrete, grout and mortar are commonly used materials which are critical to the construction industry. The materials have almost limitless uses including the construction of highways, building foundations, brickwork, and oilfield well-bore applications, to name a few. These cementitious products almost all combine at minimum a mixture of a lime cement material which is mixed with water. Other common ingredients may include sand, fly ash, silica fume, or cenospheres, to name a few.
Cellular concretes are cementitious products which are characterized by a much lower density than typical concrete, which results from air bubbles being entrained within the concrete during hardening. These low density concretes sustain impressive compressive forces, yet at significantly reduced weights, thus making the material ideal for use in roofs, above grade flooring materials and in conditions where high density concretes create soil settling problems.
Cellular concretes are typically made by mixing a foam with a cement slurry, the foam being made out of certain proteins such as ground chicken feathers and other chemical protein compositions including soaps to create a low density slurry. As the concrete cures, the air bubbles in the foam become trapped, this reducing the density of the concrete. Another method of making cellular concrete utilizes an xe2x80x9cautoclavedxe2x80x9d method where aluminum powders are put in a mold with lime concrete and water, thus creating a chemical reaction which creates hydrogen bubbles within the concrete slurry. The hydrogen bubbles are subsequently trapped during the hardening of the concrete, thus making the concrete less dense.
Unfortunately, manufacturing cellular concretes using various forms of proteins or with the autoclaved process can be expensive, time consuming and requiring specialized materials and equipment. Additionally, it typically takes a significant period of time for the cellular concrete to set, thus making it impractical for numerous commercial and industrial applications. Thus, it would be extremely beneficial and useful to have a composition and method for manufacturing cellular concretes which utilizes commonly known materials, is inexpensive and which significantly accelerates the curing process, and consequently shortens the time required for the cellular concrete to cure.
It is thus an object of the present invention to provide a composition and method for making a low density cellular concrete utilizing inexpensive materials and equipment. Thus, the materials must be readily available, non-toxic, not dangerous to handle, and stable during the manufacturing of the cellular concrete. It is a further object that the materials can be mixed on-site or off-site with conventional cement mixing equipment, and thus allows the cellular concrete to be made at remote locations where building materials are required. One particular application would be where temporary shelters are required as a result of catastrophes resulting from hurricanes, tornados, war or other disasters. The invention disclosed herein allows for production of an economical, thermally efficient, environmentally friendly, fire-resistant building material.
It is a further object of the present invention to provide a concrete material which is capable of rapidly changing viscosity during hardening, while the density remains substantially the same. Thus, in a preferred embodiment, the cellular concrete mixture can be prepared and poured in a liquid state. However, after introducing the accelerator, which is typically a sodium carbonate or sodium bicarbonate material (baking soda), the viscosity of the cellular concrete changes rapidly to a non-liquid state which cannot be poured from a 3 inch diameter by 6 inch tall cylinder mold by means of gravity. Alternative accelerators which could be used for the same purpose include all metal carbonates or metal bicarbonates, including sodium, lithium, potassium, calcium and magnesium.
It is yet another object of the present invention to provide a low density cellular concrete which utilizes power plant waste materials, and more specifically, fly ash. By utilizing an otherwise waste product, a low density cellular concrete can be made which has superior strength and is cost effective and environmentally friendly.
Thus, in one aspect of the present invention, the following materials are used in combination to create a low density cellular concrete:
1. Lime cement;
2. Water, either fresh or brine;
3. Non-ionic foam surfactant; and
4. Sodium carbonate or sodium bicarbonate accelerator.
Alternatively, sand, fly-ash, silica fume, particles, cenospheres or further materials could be used in conjunction with the aforementioned components. The foam may be produced from proteins such as ground chicken feathers and other chemical protein compositions including soaps, with a non-ionic surfactant considered a preferred material, for example, Surfonic SF 95.
Type F DSI or FGD fly ash generated as a byproduct of burning coal has also been found to be an acceptable mix ingredient. Fly ash is residue that results from the combustion of ground or powdered coal and is removed from the stack gasses with various types of air quality control equipment. Fly ash is a pozzolan: a siliceous material which, in the presence of water, will chemically combine with lime (calcium oxide) to produce a cementitious material with excellent structural properties. It has be found that about 22% by weight fly ash can be used to create a cellular concrete mix with compressive strengths similar to autoclave structural blocks used in building construction applications. Furthermore, 50% fly ash by weight has been used to create a backfill material.
In another aspect of the invention, a method is provided for manufacturing the cellular concrete material. In this process, it is critical that the cement and water are mixed first and then combined with a pre-mixed foam comprising water and preferably a non-ionic surfactant. Once the cement and foam are completely mixed, the accelerator is added to the cellular concrete mixture.